Friction — Class 8 Science NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 8 Science chapter "Friction" — 8 important questions with detailed answers for CBSE board exam preparation.

TL;DR: Free step-by-step NCERT solutions for Class 8 Science chapter "Friction" — 8 important questions with detailed answers for CBSE board exam preparation…

By Syllab.in · Updated Jun 14, 2026

Key Questions Covered:

Define friction. Why is it necessary?
Name two ways to reduce friction between surfaces.
What is static friction? Give an example.
Explain why sliding friction is less than static friction.
How does friction depend on the nature of surfaces?
Is friction always harmful? Explain with examples.
+ 2 more questions in the full chapter

Solutions Summary:

Question	Status
Define friction. Why is it necessary?	✓ Solved
Name two ways to reduce friction between surfaces.	✓ Solved
What is static friction? Give an example.	✓ Solved
Explain why sliding friction is less than static friction.	✓ Solved
How does friction depend on the nature of surfaces?	✓ Solved
Is friction always harmful? Explain with examples.	✓ Solved

Showing 6 of 8 questions

Q1: Define friction. Why is it necessary?

Friction is the force that opposes relative motion between two surfaces in contact. It is necessary because: (1) It enables us to walk without slipping, (2) Vehicles can move and stop, (3) Prevents objects from sliding, (4) Helps us hold objects. Without friction, motion control would be impossible.

Q2: Name two ways to reduce friction between surfaces.

(1) Lubrication: Use oil or grease on moving parts to reduce friction. (2) Polishing: Make surfaces smoother to decrease friction. (3) Rolling: Replace sliding with rolling motion (wheels are more efficient). (4) Air cushion: Create a layer of air or fluid between surfaces.

Q3: What is static friction? Give an example.

Static friction is the friction that acts on an object at rest, preventing its motion. Example: A book on a table experiences static friction that prevents it from sliding. The friction force equals the applied force until the object starts moving.

Q4: Explain why sliding friction is less than static friction.

Static friction acts to prevent motion and can increase up to a maximum limit. Kinetic (sliding) friction acts on a moving object and is always less than maximum static friction. Once motion begins, intermolecular bonds are broken, reducing resistance. This is why it's harder to start moving an object than to keep it moving.

Q5: How does friction depend on the nature of surfaces?

Friction depends on the roughness of surfaces: (1) Rough surfaces have high friction, (2) Smooth surfaces have low friction. The microscopic irregularities on surfaces interlock, creating friction. Polished surfaces have fewer irregularities, resulting in less friction. Material type also affects friction coefficient.

Q6: Is friction always harmful? Explain with examples.

No, friction is not always harmful. Beneficial friction: Walking on ground, writing with pencil, braking vehicles, tyres gripping roads. Harmful friction: Wear of machinery parts, energy loss in engines, rubbing causing heat. Friction is essential for life; we manage it rather than eliminate it.

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